This Week in the Universe: July 27th – August 2nd

Astrophysics and Gravitation:

Interesting Cosmic Rays Seen by Incomplete Experiment

A. Kappes for the IceCube Collaboration (2010). IceCube: Neutrino Messages from GRBs Proceedings: Deciphering the Ancient Universe with Gamma-Ray Bursts arXiv: 1007.4629v1

The under-construction IceCube Neutrino Observatory in the Antarctic has produced some exciting results already (despite being roughly a year away from officially starting).  IceCube has confirmed what had been previously suspected: That cosmic rays don’t appear to come equally from all directions in space.   Why there seems to be an asymmetric number of cosmic rays coming from certain parts of the sky is still a complete mystery, however.

For more, see Antarctica Experiment Discovers Puzzling Space Ray Pattern, IceCube spies unexplained pattern of cosmic rays, IceCube drillers train for final Antarctic season, ScienceShot: Neutrino Observatory Picks Up Cosmic Rays.

Cosmological Void Models Don’t Match Reality

Adam Moss, James P. Zibin, & Douglas Scott (2010). Precision Cosmology Defeats Void Models for Acceleration arXiv arXiv: 1007.3725v1

[W]e note that two of the most important assumptions in cosmology are those of the cosmological and Copernican principles. Therefore, in confronting void models, which blatantly violate both of these principles, with observations, we do more than just examine an unusual approach to the mystery of acceleration. We put the foundations of modern cosmology themselves to the test.

Moss, Zibin, and Scott compared the currently, somewhat, popular void model (a cosmological model based on the assumptions that our galaxy exists in a privileged position in the universe near the centre of a large, nonlinear, spherical void that was designed to help escape us from needing dark energy) to current cosmological data and found that the void model comes up lacking.  While it does not require dark energy, it also does not fit with observations of matter fluctuations, primordial power spectrum, or red shift data, making it an unreasonable cosmological candidate.

For more, see Are you the center of the Universe?, Hubble Bubble.

No Big Bang? No Problem!

Wun-Yi Shu (2010). Cosmological Models with No Big Bang arXiv arXiv: 1007.1750v1

I’ve already said my piece on this one.

For more, see TLoBP: “Cosmological Models with No Big Bang” by Wun-Yi Shu.

High Energy Physics and Particles:

Five-Body Strange Cluster

Hiyama, E., Kamimura, M., Yamamoto, Y., & Motoba, T. (2010). Five-Body Cluster Structure of the Double-Λ Hypernucleus _{ΛΛ}^{11}Be Physical Review Letters, 104 (21) DOI: 10.1103/PhysRevLett.104.212502

In 2009, KEK and J-PARC were attempting to study the creation of hypernuclei (specifically the Beryllium-Xi hypernucleus – made up of protons, neutrons, and hyperons) to see if they could play a role in neutron star physics.  Now, Emiko Hiyama and colleagues have put forth the first model to explain and predict the interactions between regular nuclei and hyperons within the hypernucleus.  If these strange quark containing atoms do form in relation to neutron stars, being able to understand their internucleus interactions should be quite important.

For more, see Nuclear physics incorporates a ‘strange’ flavor.

Heavy-Mass Nuclides Not Chaotic?

Press release from the Oakridge National Laboratory:

For more than a half century, scientists have assumed that highly excited states in intermediate- to heavy-mass nuclides are chaotic, and that data support this assumption. However, new data from the Oak Ridge Electron Linear Accelerator strongly disagree. The new results suggest that the roughly 200 nucleons inside the platinum nuclei studied act in unison to exhibit regular rather than chaotic properties. Given the relatively high energy and large number of nucleons involved, such collective behavior is totally unexpected and unexplained. A possible explanation is that an even more fundamental tenet of theory–something known as form invariance–is violated.

Interesting, but preliminary, results suggest that we need to reevaluate our models for heavy-mass nuclides.

For more, see Surprising nucleon behavior.

No Dark Matter for CoGeNT?

Peter Sorensen (2010). A coherent understanding of low-energy nuclear recoils in liquid xenon arXiv arXiv: 1007.3549v2

At IDM2010 this week, Peter Sorensen gave a talk suggesting that the detection sensitivity of experiments like XENON10 and XENON100 could be increased to rule our/address the possible light dark matter candidates that the CoGeNT collaboration was excited about in the spring.  It appears that xenon-based detectors may be much more promising tools in the hunt for light dark matter than other detectors.  Actually ruling out the CoGeNT dark matter results is still to come (but it should be feasible).

For more, see  CoGeNT dark matter excluded.

General Relativity, Quantum Gravity, et al.:

White Hole Physics Blows*

Stephen D. H. Hsu (2010). White holes and eternal black holes arXiv arXiv: 1007.2934v1

A curious paper by Stephen Hsu has been making the rounds this week.  Hsu presents isolated white holes as the time-reversal of isolated black holes, except that since white holes can not preform a process that is the reverse of Hawking radiation in black holes, he concludes that they must explode instead.  This explosion of Hsu’s isn’t based in general relativity proper but is modified by the quantum/thermodynamical aspects of white holes/black holes (see new link).  Avoiding a time-reversed-Hawking-radiation-mechanism seems like a must, to stay in agreement with thermodynamics, but it is unclear why this “explosion” would be more satisfactory.

For more, see Stephen Hsu’s confusion about white holes, Why Space Isn’t Filled with White Holes, White holes and eternal black holes (Stephen Hsu’s blog).

EDIT: Stephen Hsu has written some clarifying remarks to which Lubos has already responded in the comments.

*Sorry.

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